The Olympics should be just that, the Olympics, completely detached from any external influence and serve nothing else.
A minute of silence for this, some statement for that etc. etc. and you'll end up politicising them. Either you do it for all or for no one.
As I answered they have done this before either for events that have nothing to do with Olympics or for other Olympians who died whilst competing in the Games.
Besides, by not keeping a minute of silencing it doesn't mean that they condone or approve of what happened. It's not a binary thing. Also, the statement that by doing it they would show that such things cannot happen again, what rubbish! It happened because someone was determined to kill people, it can and will happen again regardless what we say/show/do.
I am not suggesting that they are condoning or approving of the attack. Of course it can happen again but does that mean that we should never show a mark of respect for, lets say, the victims of 7/7 right here in London because it can happen again?
Did British Fans not have a minute silence or applause for Fabrice Muamba who luckily pulled through? Or for George Best? Should I go on?